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SWEEP Report #37

Effects of Tillage on the Quality and Quantity of Surface
and Subsurface Drainage Water: Uplands

Researchers: 
R.G. Kachanoski, R. Rudra, and E. Pringle, University of Guelph, Guelph, Ont.

Executive Summary

Evaluation Summary (Tech. Transfer Report Summaries)

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Associated SWEEP/LSP Research

 

 

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Completed: January, 1992

Key Words:

water quality, tillage, surface drainage, subsurface drainage, surface runoff, tile drainage, no-till, moldboard plow, nitrate nitrogen, phosphorus, macropore transport, leaching

Executive Summary

A study was undertaken to determine the effects of tillage system on the quantity and quality of surface runoff and tile drainage water. Previous studies have suggested that the increased infiltration and occurrence of macropores in no-till systems may increase the risk of movement of chemicals to the groundwater. Thus, no-till systems may solve one problem (surface water quality), but create another problem (groundwater quality).

The study was carried out on the long term no-till - moldboard plough comparison established by Don Lobb, a conservation farmer near Clinton, Ontario. The soil at the site is a sandy loam. Three tile lines in each of the two tillage systems were instrumented for monitoring tile flow quantity and the concentrations of nitrate nitrogen and phosphorus.

Multi-level groundwater samplers were also installed in each treatment, and soil coring and the application of tracers (chloride) were used to track the movement of soluble chemicals. Detailed solute transport experiments under controlled application of water were also carried out to characterize the soil transport properties. The installation of equipment was started in the fall of 1988 and finished in spring of 1989. The site was planted with corn in 1989 and soybeans in 1990.

Surface runoff was monitored by installing runoff collection flumes on selected soil landscape positions within the study field. Rainfall simulation studies and characterizations of the hydraulic soil properties controlling surface runoff were also carried out in cooperation with other studies.

No significant tile flow was recorded until late fall 1989. From Oct. 1, 1989 to Oct. 1, 1990 a total of 121 cm of precipitation was recorded. Total tile flow amounted to approximately 19.0 cm with no significant differences between tillage systems. Movement of water below the tile line was significant and estimated at 49 cm of water.

No-till had significantly higher average concentration and water flux averaged concentration of NO3-N in the early spring and fall periods compared to moldboard, but the reverse was true in the late fall. The average concentrations in both systems exceeded the drinking water quality limit of 10 mg/l N03-N. The average concentration was 10.7 mg/l N03-N in both systems.

Total nitrogen leaching from the 1989 corn crop was estimated at 80 kg N/ha and 50 kg N/ha in the no-till and conventional till systems respectively. The increased N leaching in the no-till was attributed to a higher N soil test in the no-till system and a requirement for less N fertilizer than the moldboard systems. Both systems had the same fertilizer applied (160 kg N/ha). The amount of N lost by leaching in each replicated plot was significantly correlated to the difference between the fertilizer N applied and the fertilizer amount required according to the N soil test.

Detailed transport studies indicated more macropore transport in the moldboard plough system than the no-till system. However, the average solute transport velocity was faster in the no-till, which was attributed to increased occurrence of blocked pore domains.

The no-till system should not result in an increased risk of chemical contamination of our groundwater resource. If the nitrogen soil test is used to determine fertilizer requirements then the occurrence of over-application of N fertilizer should be significantly reduced in all tillage systems.

Surface water runoff from both the no-till and moldboard treatments was negligible at this site. This was attributed to the very high infiltration rates of the sand-loam soil. Runoff simulation indicated that increased water runoff would be expected in the no-till treatment for very large rainfall events. However, total phosphorus loss would be 2 to 4 times lower than the moldboard treatment.

Dissolved ortho-phosphorus and nitrate N in runoff water was also very low in the sandy-loam textured soil. However, runoff simulation on a clay-loam textured part of the field indicated that ortho-phosphorus in the runoff was significantly higher in the no-till compared to moldboard treatment. This, combined with an increased runoff volume from the no-till may be a problem in heavier textured soils.

 

Evaluation Summary

(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank, Co-Chairs)
 

The study was conducted to determine the effects of tillage systems on the quantity and quality of surface runoff and tile drainage water. The plots were located in Huron County on a long term no- till - moldboard plough comparison. Tile lines in each of the tillage systems were monitored for flow quantity, and the concentration of nitrate nitrogen and phosphorus. Multi-level groundwater samplers were installed to track the movement of soluble chemicals. Surface runoff was monitored through the use of runoff collection flumes and rainfall simulation studies were undertaken to characterize the hydraulic soil properties.

The results of the 2-year study showed that tile flow was no different between the two tillage systems. No-till had significantly higher average concentrations of nitrate nitrogen in the early spring and fall compared to the moldboard but the reverse was true in the late fall (both systems had concentrations that exceeded drinking water standards). More N leaching occurred in the no-till than moldboard plough treatment. The increased N leaching in the no-till was attributed to a higher N soil test in the no- till system and a requirement for less N fertilizer than the moldboard system (both systems received the same amount of fertilizer). The amount of N lost by leaching was correlated to the difference between the fertilizer N applied and the fertilizer amount required according to the N soil test.

More macropore transport was evident in the moldboard system than the no-till. However the average solute transport velocity was faster in the no-till (may be due to the increased occurrence of blocked pores).

Surface runoff was negligible for both treatments (sand-loam soil). Out of 121 cm of rainfall that fell between Oct./89 and Oct./90, 19 cm left the site as tile flow and an estimated 49 cm moved below the tile lines (in both tillage systems). Rainfall simulation trials indicated that increased water runoff would be expected in the no-till system for very large rainfall events. However, total phosphorus loss would be 2-4 times lower than the moldboard system. Runoff simulation on a clay-loam part of the plot indicated ortho- phosphorus in the runoff was higher in the no-till compared to the moldboard. With an increased runoff volume from the no-till, this may be a problem in heavier textured soils.

Comments:

An excellent study that contains a lot of good information about water quality and tillage systems for a sandy-loam soil. The higher runoff in the no-till treatment found in this study contrasts with other American studies, particularly at Coshocton, and with the results of SWEEP Report #30 (P. Neave).

Associated SWEEP/LSP Research:

  • SWEEP Report #17 - Effect of Ammonia on Soil Properties and Relevance to Soil and Water Quality

  • SWEEP Report #18 - Effects of Management on Soil Hydraulic Properties

  • SWEEP Report #23 - Processes Involved in Mobilization of Phosphorus in Different Farming Systems in Southwestern Ontario: Nutrient Levels in Plant Tissues and Soils

  • SWEEP Report #30 - The Response of Soil Microflora and Fauna to Spring Plowing of Zerotill and Pasture Soils

  • SWEEP Report #37A - Appendix I-X of SWEEP Report 37

  • SWEEP Report #45 - Management of Farm Field Variability. III. Effect of Tillage Systems on Soil and Phosphorus Loss

  • SWEEP Report #51 - Loss of Nitrogen by Microbial Denitrification, Nitrification, Surface and Tile Runoff: Relation to Tillage Method

  • SWEEP Report #60 - The Effect of Conservation Tillage Practices on the Losses of Phosphorus and Herbicides in Surface and Subsurface Drainage Waters

Future Research: ( ) indicates reviewers suggestion for priority, A - high, C - low.

(A) More work needs to be done on a variety of soils in order to understand the infiltration/runoff behaviour under different tillage systems.

 

 

 

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Created: 05-28-1996
Last Revised: Thursday, May 19, 2011 03:01:25 PM